If it wasn’t clear before, it has become all too clear after two weeks that the Trump administration poses a serious threat to liberal democracy.

What we have witnessed since January 20 has little precedent in U.S. politics. A raft of commentary since the election—from Masha Gessen’s “Autocracy: Rules for Survival” to historian Timothy Snyder’s “20 Lessons from the 20th Century on How to Survive in Trump’s America” to a recent op-ed by Miklos Haraszsti, the Hungarian former anti-communist dissident, likening Trump to Hungary’s current authoritarian-leaning leader, Viktor Orban—has fittingly sought to explain and confront Trumpism by turning to authoritarian regimes abroad.

Many political scientists share these writers’ concerns. As Steven Levitsky and Daniel Ziblatt recently wrote, a well-designed constitution alone cannot constrain authoritarian tendencies.Daniel Nexon has summarized the threats that existing domestic and international institutions now face. And political economist Daron Acemoglu has suggested that civil society must act as the last line of defense against the autocratic tendencies of the Trump administration.

Meanwhile the Trump administration continues to issue disturbing executive orders at a furious pace, setting in motion the promised Mexican wall and Muslim ban, reorganizing the National Security Council to replace the Chairman of the Joint Chief of Staffs with white nationalist Stephen Bannon, and continuing to wage war on the independent media.

We will surely see a proliferation of resistance movements over the next four years. The nationwide women’s marches of January 21 were the first sign. The rapid upsurge of protest against last week’s immigrant ban is another. Protests, marches, and rallies have been key channels for resistance to hybrid-regime autocrats such as Turkey’s Erdoğan and Russia’s Putin, and the United States has its own long history of civil disobedience. Progressive voices from Frances Fox Piven to Robert Reich have already begun putting forward ideas of how resistance to the Trump administration can be organized.

Surprisingly, one name has been largely absent from these conversations: Gene Sharp. A longtime and prolific theorist of nonviolent direct action, Sharp first came to international prominence in 2000, when Serbian democratic activists inspired by his ideas helped to depose Slobodan Milosevic, as portrayed in the powerful documentary Bringing Down a Dictator. Sharp’s name resurfaced in 2011, when the activists of the Arab Spring found inspiration in his books and pamphlets, and CNN referred to him as “a dictator’s worst nightmare.”

Until now, Sharp’s ideas have largely been applied in authoritarian contexts abroad, whether in the Middle East, post-Communist Europe, or elsewhere. But under Trump, Sharp’s ideas have become all too relevant to the contemporary United States. What insights could American activists today glean from his work about the possibility of resisting the Trump administration?

Sharp has codified an approach to nonviolent civil resistance that draws on the lessons of Gandhi, King, Havel, and others. Sharp’s theory of power emphasizes that authoritarianism is premised upon the obedience of the population and the collaboration of individuals with those in power. His basic point is that concerted nonviolent resistance can strip the moral and political authority of an authoritarian regime.

Compliance is key to the legitimacy of any regime, and Sharp offers a handbook for how to effectively withhold it. His compendium of 198 Methods for Nonviolent Action presents a wide range of techniques—from letters and speak-outs to boycotts, strikes, sit-ins, blockades, and slowdowns—that citizens can employ to refuse an illegitimate authority. When coupled with more traditional forms of protest, these tactical disruptions of the normal functioning of the system can place immense pressure on dictators. Sharp treats authoritarian regimes as fragmented coalitions held together by a tenuous obedience to authority. Once the perception of invincibility is removed, such regimes can rapidly disintegrate.

If Machiavelli’s writings envision an “economy of violence” (per Sheldon Wolin), then Sharp can be considered Machiavelli’s heir, in form if not in content. Sharp’s work is organized around an economy of nonviolence, understood as a political praxis that, when wielded by committed and organized groups, can radically change the distribution of power in a society.

While drawing from the moral tradition of pacifism, Sharp’s appeal to nonviolent resistance is a pragmatic one: he largely sidesteps normative discussions in favor of a sober, one could say realist, analysis of the dynamics of political power. Concerted nonviolence, he finds, is simply more effective in challenging authoritarian regimes than armed uprising.

Since the 1990s, Sharp’s ideas have spread rapidly. His From Dictatorship to Democracy, first published in English and Burmese in 1993, was soon translated and circulated in over forty countries. It influenced figures like Srdja Popovic of the Serbian group Otpor, which helped depose Milosevic, and activists of the “color revolutions” of the early-mid 2000s, Lebanon’s Cedar Revolution of 2005, Iran’s Green Movement in 2009, and the Egyptian and Tunisian revolutions of 2011.

Sharp’s notoriety has made him enemies across the political spectrum. Though Sharp’s Albert Einstein Institute is a wholly independent operation, his books have become important resources in the repertoire of U.S. “democracy promotion.” Autocrats have accused him of propagating revolutionary (or “counterrevolutionary”) ideas. Left critics claim that his work assists U.S. clandestine efforts to promote soft regime change abroad, though Sharp denies the latter point, with figures including Noam Chomsky and Howard Zinn coming to his defense.

Sharp’s work furnishes a practical toolkit for organizing resistance to Trump’s authoritarianism. Nonviolent resistance has a long history in the United States, and Sharp is above all a pithy synthesizer of widely circulated movement wisdom. Many recent initiatives across the country, from Black Lives Matter to the water protectors’ camp at Standing Rock, have already put to use the tactics Sharp advocates. Leaders of the NAACP were recently arrested for sitting in at the office of Senator Jeff Sessions in protest against his nomination as Attorney General. Immigrant-rights groups linked to the sanctuary movement are preparing to practice civil disobedience in response to a threatened crackdown from the Trump administration.

Whether and how these various protest initiatives can coalesce is an open question. Sharp’s work is useful for thinking not just about the tactics of resistance but about a strategy centered on the regime itself. While Sharp’s advice is relevant to all forms of citizen action, it is most relevant to thinking about challenging dictatorships rather than “flawed democracies.” But if Gessen and others are right, and if the furious trend of the past weeks is any guide, then we are closer to authoritarianism than most previously suspected.

The distinctive features of the U.S. constitutional system will hopefully furnish us with opportunities unavailable to citizens of Russia, Hungary, or Turkey—though we can no longer take this for granted. Regardless, seizing what opportunities remain will require an upsurge of democratic citizen action. And if such a civic uprising is going to succeed, it will require savvy attention to the themes highlighted by Gene Sharp.